1. Field of the Invention
This invention relates generally to phonograph record players, and more particularly is directed to an improved phonograph record player control mechanism for effecting lead-in-movement of a tone arm from an elevated rest position outside the perimeter of a turntable to a selected set-down position on a record supported by the turntable so as to commence a play operation, and for effecting a return movement of the tone arm to its rest position upon the termination of the play operation.
2. Description of the Prior Art
In a known so-called automatic phonograph record player, for example, as disclosed in detail in U.S. Pat. No. 3,438,635, a control mechanism is provided for effecting automatic lead-in movement of the tone arm from an elevated rest position outside the perimeter of the turntable to a selected one of a plurality of set-down positions of the stylus on a record supported by the turntable so as to commence a play operation at the selected set-down position, and for automatically effecting a return movement of the tone arm to its rest position upon termination of the play operation. In such control mechanism, a control gear is turned during the lead-in and return operations and is formed wth a radial cam on its upper surface and a cam groove in its lower surface. The cam groove is engaged by a follower on one end of a link member which is longitudinally reciprocable and which, at its other end, is formed with a cam surface for controlling an arm lifter by which raising and lowering of the tone arm is effected. The radial cam on the upper surface of the control gear is engaged by a follower depending from a cam plate which is guided by pin and slot mountings for longitudinal reciprocation in a direction that extends through the rotational axis of the control gear, and a spring acts on the cam plate to urge the latter in the direction for maintaining contact of its follower with the radial cam. An oblique cam surface is formed on the cam plate and is engageable by a follower at one end of a link which is guided, by pin and slot mountings, for longitudinal reciprocation at right angles to the reciprocation of the cam plate, and which, at its other end, is connected to the tone arm assembly for effecting swinging of the tone arm in response to longitudinal movement of the link. In order to provide for selection of the set-down or start-of-play position, the known control mechanism includes a rotatable selector knob connected through a link with a rotatable disk which is provided with a plurality of abutments that can be selectively operatively positioned for engagement by a pin on the cam plate in response to turning of the selector knob.
The above described known phonograph record player control mechanism has a number of disadvantageous characteristics. To begin with, the pin and slot mountings, by which the cam plate and the link carrying the follower for engagement with the cam surface on such cam plate are guided for longitudinal reciprocation at right angles to each other, inherently have a substantial degree of lateral play which materially affects the accuracy of the set-down position of the stylus depending from the pickup at the free end of the tone arm. In other words, by reason of the described lateral play, substantial variations can occur in the set-down position established by the engagement of the pin on the cam plate with a selected one of the abutments on the set-down position selecting disk. Further, by reason of the described relatively complex mechanical arrangement by which swinging of the tone arm is controlled during its lead-in movement, it is inevitable that, in the manufacture and assembly of the parts of such complex mechanical arrangement, variations will occur from one record player to the next in the set-down positions of the tone arm corresponding to the several abutments on the set-down position selecting disk. Moreover, no provision is made for effecting the fine adjustment of such set-down positions so as to compensate for the variations occurring during manufacture and assembly. Furthermore, in the described control mechanism, the longitudinally reciprocable link carrying the follower which is engageable with the cam plate for effecting the lead-in movement of the tone arm to the desired set-down position remains connected to the tone arm assembly during the subsequent play operation and thus may adversely influence the tracking of the record groove by the pickup stylus.